EP0132653B1 - Circuit arrangement for generating characters or graphic patterns by means of output units of matrix printing devices - Google Patents

Description

The invention relates to a circuit arrangement according to the preamble of patent claim 1.

Printing output devices of data processing systems are increasingly being trained as matrix printers with the increasing need for universal character design (capitalization, bar code printing, graphics, etc.). Compared to type printers, with the appropriate resolution and using loadable electronically stored character sets, almost any characters can be created on matrix printers.

With matrix printers, the resolution of a print character is limited on the one hand by the size of the smallest printable unit - a dot - or its technical feasibility and geometric arrangement, on the other hand by the maximum write frequency for a given print performance and by the memory required for the electronic image of a character. To achieve good print quality, a high resolution is absolutely necessary, especially for printed characters that require bevels or curves within the character shape. A low resolution can lead to a step-like representation of individual written elements.

From DE-OS 24 57 884 a mosaic printer with line-by-column and column-by-line, excitable by binary signals of the character generator print types in a matrix arrangement is known, which contains a delay device for delaying the binary signals in successive lines.

The delay device allows the printed characters to be tilted.

A serial matrix printer is also described in US Pat. No. 3,330,208, in which the actuation signals for the printing elements can be delayed for different lengths depending on the desired inclination of the character to be printed.

US-A-4 321 610 describes a matrix printer which, when printed, can shift individual character elements in order to increase the horizontal resolution and thus to improve the font quality. This printer works with a fixed displacement and requires two storage units in order to store non-displaceable and displaceable drawing elements. When a character is printed out, the character elements are then read either from the first storage unit or from the second storage unit.

In order to improve the font quality, it is also known (cf. EP-A-40 313) to individually shift individual character elements when printing. With this solution, too, an increased storage capacity is required to record the individual shifts.

The object of the invention is to provide a circuit arrangement for generating characters or graphic patterns via .. output units of mosaic printing devices or devices operating according to the raster principle, which makes it possible to increase the horizontal resolution of a character without increasing the writing frequency and without additional storage capacity and thus the Improve font quality.

This object is achieved in a circuit arrangement of the type mentioned at the outset in accordance with the characterizing part of the first claim.

Further advantageous embodiments of the invention are characterized in the dependent claims.

By organizing the character elements in character fields with group identifiers in which the individual character elements are identified by identifier, it is possible to shift individual character elements during printing by using a corresponding recognition arrangement via the addressing and control unit and thus to optimize the typeface. If one takes into account that most characters do not occupy all the memory cells of a character field - especially the marginal columns and marginal rows of a character field are rarely occupied by dots to be printed due to the required spaces between the next character or in the next line - these marginal columns and / or Margin lines can be used to store the identifier.

A particularly simple control option for the individual character elements is obtained by dividing the character fields into a first group of character fields with movable character elements and a second group of character fields with non-movable character elements and distinguishing the two character field groups by a group identifier. The first binary character of the first line and column of the character field can serve as the group character.

As a result of this type of assignment, the marginal columns and marginal rows in the character fields can also be used for the assignment with character elements to be printed, for which otherwise no movable character elements are provided within the character field.

Such character fields with non-displaceable drawing elements are necessary in any case to z. B. to represent continuous lines, curves or special characters of a larger format, which extend over several writing points or lines.

If character fields are used in which at most one character element is binary in each column is stored, the first line of each column serving as a binary character, the circuit arrangement can be designed particularly simply in connection with a first pressure register and a second delay pressure register. When printing, the character field is read out column by column and temporarily stored in the print registers. When a character element to be shifted, identified by an identifier, is recognized, the delay pressure register is then read out, and in the case of a character element this need not be corrected, the print register.

According to one embodiment of the invention, the two groups of character fields can be easily distinguished by arranging a first column register which is linked to the matrix memory and into which the first column of each character field is read. By simply linking the first memory cells to the column clock of the first column, a signal for recognizing the binary character used as a group identifier can be generated.

• Fig. 1 eine schematische Darstellung eines Zeichenfeldes mit zugehöriger Belegung duch Zeichenelemente,
• Fig. 2 eine schematische Darstellung einer Ausführungsform der erfindungsgemäßen Schaltungsanordnung in einem Laserdrucker.

An embodiment of the invention is shown in the drawings and is described in more detail below, for example. Show it

• 1 is a schematic representation of a drawing field with associated assignment by drawing elements,
• Fig. 2 is a schematic representation of an embodiment of the circuit arrangement according to the invention in a laser printer.

A laser printer not described here in detail, as it is known for. B. is known from US Pat. No. 4,311,723 contains, as can be seen from FIG. 2, a laser source L, an associated acousto-optical deflector AO, a polygon mirror PS and the associated record carrier AT. The actual control means for the laser printer is formed by the acousto-optical deflector AO, which in principle corresponds to the print head of a dot-matrix device. This acousto-optical deflector is controlled via the circuit arrangement according to the invention described in more detail below.

It essentially consists of a matrix memory MS in which the individual representable characters are stored in binary form as line or pattern-describing binary character strings individually in character fields of the same size which are constructed in a matrix-like manner as column elements or line elements. This matrix memory MS is controlled by an addressing and control unit AS which addresses the matrix memory MS in a known manner via an addressing memory ADS and thus calls up the character to be displayed column by column from the matrix memory and the acousto-optical deflector via a processing and detection arrangement which will be described in detail later AO controls.

The individual character elements to be displayed are now stored in the matrix memory MS in character fields ZF (FIG. 1) of the same size in the form of binary characters. For example, a character field has a resolution of 18 x 24 points for a character of the size 1/10 x 1/6 inches, which corresponds to 432 memory locations, which correspond to the crossing points of the rows and columns coordinates Z1 to Z24 and S1 and S18 in FIG. 1 . The character "slash" shown is defined by the assignment of the corresponding memory locations within the character field ZF. In order now to optimize the typeface and thus smooth the represented "/" while preventing gradations, individual drawing elements, in this case the drawing elements with the coordinates S12, Z3; S11, Z5; S10, Z7; etc. can be printed out by means of the delayed activation of the acousto-optical pick-up AO via the control arrangement AS linked to the matrix memory. B. results by half a character division.

In order to be able to easily accomplish this shift, the individual characters to be displayed are stored within the matrix memory as two groups of character fields ZF, which are differentiated according to whether character elements are stored in the character field that are to be shifted via the circuit arrangement and thus corrected. In the case of the character fields, this is accomplished by assigning a group identifier GK at the coordinate position Z1, S1 of the character field ZF. An assignment with a "binary" one at the position described denotes a character field which contains character elements to be corrected. An assignment with "zero" then corresponds to a drawing field without drawing elements to be corrected or moved.

Such identification of the character fields via an identification bit referred to as a "group identifier" enables characters to be printed within a character set with a printer controller modified in accordance with the invention, which characters also occupy the first line and the first column within the character field. Such an assignment is e.g. B. necessary if characters are to be printed, which extend over several character fields z. B. solid lines or the like. When the character field is occupied in this way, it is therefore only necessary to keep the first memory cell defined by the coordinates Z1 and S1 free for the group identifier. In order to be able to use this storage space as storage space for a drawing element in special cases, it is also possible to separate the group identifier outside the drawing field Save register. However, this leads to a slight increase in the storage space requirement.

In the example shown in FIG. 1, in which character elements to be corrected within the character field are stored, identification bits designated as “identifier” are stored in the first column and the first line of the character field in order to identify these character elements to be corrected by displacement. By assigning these identifier bits in the first column and the first line, the printer controller connected downstream can be informed that the points lying in the intersection points of the identifier bits - in this case offset by half a division - should be printed later. In the example shown, the character fields are organized in such a way that only a maximum of one single character element is stored per column S1 to S18. As a result, it is possible in this case to store the identifier (identifier bit) only in the first line Z1, without this leading to ambiguities within the character field ZF. If character fields are to be used in which several character elements are stored per column, this can possibly lead to an undesired correction of an edge point. In this case, the point must not be corrected, which in turn can be taken into account when creating the character shape and the associated correction points.

In the example shown, the identifier bits are arranged in line Z1 to identify the character elements to be corrected. Of course, it is also possible to arrange the identifier bits in column S1 or, when using character fields in which several character elements are arranged per column, to use both the first column and the first row together as storage locations for the identifier characters. The drawing elements can be corrected by moving them in the row direction as well as in the column direction.

The function of the circuit arrangement will now be described in detail below with reference to FIG. 2.

To control the acousto-optical deflector AO, the character to be displayed is read out column by column with the aid of the addressing and control device AS from the matrix memory MS. This reading takes place in cycles of a column cycle which is generated by the addressing and control unit AS and whose frequency depends on the desired writing speed. When reading a character from the matrix memory, the corresponding character field ZF is first addressed and transferred to all 24 bits of the first column S1 of the character field in a first column register ES. A set bit at the position ES1 of the first gap register indicates that characters stored in the character field ZF and characters to be printed contain elements to be corrected. This "correction bit" is identified via an AND link U1 which links the memory location Z1 of the first gap register ES with the column clock driving the first gap register ES. After the first column of the character field has been stored in the first gap register ES, two print registers DR and VR, which are located in connection with the matrix memory, are set via the addressing and control unit. The pressure registers DR and VR are linked on the output side to the acousto-optical deflector AO and serve as a buffer. By assigning the first gap register ES at position ES1 with a binary "1", it is shown that there is no print information in the first line of the character field ZF.

With the second column clock, the second column S2 is read from the character field ZF stored in the matrix memory MS and transferred to the print registers DR and VR.

The structure and size of the pressure registers DR and VR correspond to the first gap register ES.

Depending on whether the drawing element stored in the print registers DR and VR should be delayed, ie corrected or not, either the print register DR or the delayed print register VR is now controlled via the addressing and control unit AS. The delayed print register VR is activated with a time delay compared to the activation of the print register DR, namely by a time which corresponds to approximately half a column width, so that the displacement of the drawing elements to be corrected, which is represented by arrows in FIG. 1, results. The decision as to which of the two print registers DR and VR is to be set and thus whose content is to be transmitted to the acousto-optical deflector is made by comparing the content of the first memory location of the delayed print register VR, VR1 with the content of the memory register Z1 of the first gap register ES via the Undlink U2. If the column stored in the print registers DR and VR contains a character element to be corrected, the identifier in the memory location VR1 and DR1 is assigned a binary "one". Since in this case the first gap register in its first memory location ES1 is simultaneously assigned a binary "one" and thus indicates that the called character field ZF is a character field with characters to be corrected, only the delayed print register VR is used for printing operated. Then z. B. the column addresses increased by a counter and thus the next column from the called character field ZF of the matrix memory MS via a generally customary internal column counter in the cycle of the column clock accessed. After storing the first column in the first column register via the re-connection U1, it is found that it is a character field which does not contain a character element to be corrected, the storage location ES1 of the first column register ES is one for the duration of the reading of the character field Binary characters are logically "zero". The acousto-optical deflector AO is thus controlled solely via the print register DR, a binary character "ONE" recognized when the first column of the character field is stored being interpreted as pressure information for a character element in this first column. With the exception of the first character of the first column and the first line of the character field ZF, all the bits stored at the location DR1 of the print register DR and thus taken from the first line of the character field are now interpreted as print information.

In the examples shown, the printing registers are written in parallel for all 24 character points in a column. Of course, this can also be done in subsets or in series.

For matrix printers in which the horizontal writing frequency can be increased without problems, as z. B. is the case with laser printers, the stroke width is also in intermediate sizes, z. B. 1 1 / 2.2 1/2 etc. point sizes selectable. This makes it easier to optimally adapt to machine-readable print characters or closely tolerated characters such as bar codes.

Claims (5)

1. A circuit arrangement for producing characters or graphic patterns via output units of mosaic printers or devices operating in accordance with the raster principle, in which a recording means (L) is moved row by row along a data carrier (AT) in order to produce image points, with a matrix store (MS) in which the individual characters are stored in binary form, as binary character sequences, descriptive of lines or patterns, individually in equal size character arrays (ZF) of matrix-like construction, as character elements arranged in columns and rows, and with an addressing and control unit (AS) which reads the character elements, stored in binary form, from the matrix store (MS), converts said character element into the drive signals for the recording means, and as and whe necessary produces a displaced image point via delay device, characterised in that first and second groups of character arrays (ZF), provided with group identification characters (GK), are provided, where the first group of character arrays are assigned displaceable character elements, characterised by code characters (KZ) and the second group of character arrays are assigned non-displaceable character elements, and that a recognition arrangement (Ul, U2) is provided which detects the group identification characters (GK) and the code characters (KZ), and converts these into drive signals for the adressing and control unit (AS), so that when a character element, which is to be displaced, is read from the matrix store (MS), the recording means (AO) is driven in delayed fashion in relation to the drive of the recording means whei a character which is not to be corrected is read out, and thus there is a displaced formation of the image point along the row and/or column.

2. A circuit arrangement as claimed in claim 1, characterised in that the first binary character of the first row and column of the character array (ZF) serves as group identification character (GK).

3. A circuit arrangement as claimed in one of the claims 1 or 2, characterised in that the binary characters of the first row and/or column of the character arrays (ZF) are provided as code characters.

4. A circuit arrangement as claimed in one of the claims 1 to 3, characterised in that a maximum of one character element is stored in binary form in the character arrays (ZF) in respec of each column, where the binary characters of the first row of each column serve as code characters (KZ), that a first printer register (DR), connected to the recording means (AO), and a second delay printer register (VR) are provided, and that in order to print a character element which is to be displaced, the delay printer register (VR) is driven via the addressing and control unit.

5. A circuit arrangenent as claimed in claim 4, characterised in that a colunn register (ES) is provided which intermediately stores the first columns of each character array (ZF) during the read-out procedure and that the column register (ES) is assigned a logic arrangement which recognises the group identification character (GK).

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